How can I accept mail from only one domain in smtp-gated?

I need a Perl-compatible regular expression for filtering my email with smtp-gated. I only want to allow one domain ('mydomain.com') and reject everything else. How do I do this in a foolproof way? (regex_reject_mail_from)

I know this question halfway belongs on serverfault, but basically it's a Perl regex question so I think it fits stackoverflow more.

EDIT:

This should match so I can reject it:

"Someone" <someone@somedomain.com>

This should not match:

"Me" <me@mydomain.com>

This shouldn't match also:

you@mydomain.com

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I'd suggest the following:

\b[A-Z0-9._%+-]+@(?!mydomain\.com)[A-Z0-9.-]+\.[A-Z]{2,6}\b

Use the /i option to make it case-insensitive.

This will match most valid (and some invalid) e-mail addresses that don't have mydomain.com after the @. Keep in mind that e-mail validation is hard with regexes.

If your regex is going to be applied to the MAIL FROM line in the MTA communication then you do not need to concern yourself with the full 'email address' specification. MAIL FROM lines are just the email address enclosed in '<>', so any regex that tests for @mydomain.com> should work.

\b(?:"[ a-zA-Z]+")?\s*<?[a-zA-Z0-9_.]@(?!mydomain\.com)\w+(?:\.\w{2,})+>?\b

UPDATE: Note that this regex is fa{9,}r from being perfect. Check the official regex for email addresses for more info (Scroll down to the <p/> titled RFC 2822).